There have been a few patents which teach electronic circuit arrangements exhibiting negative resistance. U.S. Pat. No. 3,358,153, Dec. 12, 1957 (Poo), for example, uses a pair of bipolar transistors of the same conductivity to obtain two terminal negative resistance circuit. A positive feedback in the circuit produces a negative resistance which is essentially ohmic in nature, i.e. an equal negative resistance being developed for very low as well as high frequencies. Its behaviours are defined clearly by the static I-V curve shown in the drawings of the patent.
Canadian Pat. No. 924,390, Apr. 10, 1973 (Stanley) also teaches an electrical network having two terminals and exhibiting negative dynamic resistance characteristics. The network includes a field-effect transistor and a bipolar transistor in that the field-effect transistor controls the bias of the bipolar transistor whereby the I-V characteristics curve contains a region of negative resistance.
As in the above referenced patents, the present invention uses two active devices, e.g. bipolar junction transistors or field-effect transistors or a combination of both in its negative admittance network. However, unlike in the prior art patents, the two active devices of the present invention are always of different conductivities to each other, irrespective of the kind of active devices used.
By selecting the kinds of active devices and the choice of the various circuits components, a wide range of operating characteristics can be obtained.